This section endeavors to supply a context or background for the various exemplary embodiments of the invention as recited in the claims. The content herein may comprise subject matter that could be utilized, but not necessarily matter that has been previously utilized, described or considered. Unless indicated otherwise, the content described herein is not considered prior art, and should not be considered as admitted prior art by inclusion in this section.
Chemical vapor deposition (CVD) is a chemical process designed to produce high-performance solid materials used in semiconductor processing. Typically, CVD techniques expose a substrate to one or more volatile precursors that decompose and/or react on the surface of the substrate to produce the deposited material. By-products may be produced and, subsequently, removed via gas flow through the reaction chamber. As non-limiting examples, CVD may be used to deposit layers of polysilicon, SiO2, Si3N4, SiNH, HfO2, Mo, Ta, Ti, TiN and W.
Atomic layer deposition (ALD) is another thin film deposition technique. ALD uses precursors (chemicals) that react with the surface separately in a sequential manner. A thin film is deposited by repeatedly exposing the precursors to the substrate. While similar in chemistry to CVD, ALD breaks the CVD reaction into two or more half-reactions, maintaining the precursors separately during the overall ALD process. ALD enables atomic scale deposition control and can achieve growth on the order of one monolayer or less per cycle. Separation of the precursors may be obtained by utilizing a purge gas (e.g., N, Ar) after each precursor to remove excess precursor from the process chamber and reduce or prevent parasitic CVD processes (e.g., extra deposition on the substrate via CVD). As non-limiting examples, ALD may be used to deposit layers of Al2O3, TiO2, SnO2, ZnO, HfO2, TiN, TaN, WN, NbN, Ru, Ir, Pt and ZnS.